Adaptive Beamforming for SAR Control in Mobile Devices
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Solution Overview
Problem
Mobile devices, such as cellular modems, face challenges in meeting specific absorption rate (SAR) requirements due to variable orientations with the human body, leading to limitations in maximum power, data rate, and physical size, as conventional approaches focus on peak radiation points rather than averages.
Innovation Solution
A system and method utilizing adaptive beamforming with fractional power amplifiers, return power detectors, and a beamformer unit to shape the transmitted beam pattern, minimizing reflected power and adjusting parameters based on return loss sampling information to maintain SAR compliance across different orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional antenna radiation limits are set based on peak radiation points, then SAR requirements are met, but maximum power, data rate, and device size are limited
Solution Approach 1:
The patent changes the parameter basis for SAR compliance from peak radiation points to average total radiated power (TRP). By setting antenna radiation limits based on average TRP rather than peak values, the system allows higher maximum power and data rates while maintaining SAR compliance through statistical averaging over multiple orientations and positions.
2Reliability
If antenna radiation limits are set based on peak radiation points, then SAR requirements are met, but device physical size is limited
Solution Approach 1:
The patent changes the parameter basis for SAR compliance from peak radiation points to average total radiated power (TRP). By setting antenna radiation limits based on average TRP rather than peak values, the system allows for larger device sizes and more antenna elements while maintaining SAR compliance through statistical averaging.
3Device complexity
If fixed orientation relationship between handset and user head is assumed, then radiation pattern shaping is simplified, but adaptability to variable orientations is reduced
Solution Approach 1:
The patent implements dynamic adaptability by measuring return loss across multiple antenna elements and orientations, then using beamforming techniques to adaptively shape the radiation pattern based on the actual device orientation and position relative to the user's body. This allows the system to maintain SAR compliance regardless of how the device is held or positioned.
Solution Approach 2:
The patent uses return loss measurements as feedback to dynamically adjust the beamforming weights and radiation pattern. By continuously monitoring the reflected power from the user's body and adjusting the antenna phase and amplitude accordingly, the system adapts to variable orientations while maintaining SAR compliance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively maximizes effective radiated power while keeping radiation levels below SAR limits, reducing radiation exposure and maintaining transmission quality, even with non-fixed absorption spots relative to the device.
Implementation Method 1
a beamformer unit configured to provide an adaptive beam shaping pattern to the fractional power amplifiers, the adaptive beam shaping pattern configured to shape a transmitted beam pattern to minimize an amount of transmitted power reflected back to at least one of the antennas
Implementation Method 2
respective returned power detectors coupled to a transmission path between each of the at least two antennas and respective fractional power amplifiers, wherein the respective returned power detectors provide return loss sampling information to the beamformer unit
Data Source
AI summary
A system may include a modifiable mobile device having at least two antennas coupled to fractional amplifiers, with returned power detectors. A beamformer unit provides adaptive beam shaping pattern, and a baseband processor provides beam pattern requirements, wherein the beamformer unit modifies the beam pattern requirements with return loss sampling information to shape the adaptive beam pattern so that a transmitted beam pattern minimizes transmitted power reflected back to the mobile device. A method may include regularly measuring a return power level, if output power is greater than a specific absorption rate level, comparing the return power level to a first threshold, else implementing mobile transmit diversity (MTD), and repeating. If the return power level is greater than the first threshold, implementing a MTD combined with reflection-based beamforming that modifies beam pattern requirements of the mobile device with return loss sampling information to create an adaptive beam pattern.